Many vehicles utilize hybrid drive technologies, in that a vehicle utilizes both an internal combustion engine and at least one electric motor to power the vehicle, and are often referred to as hybrid electric vehicles. In smaller vehicles, such as automobiles and light-duty trucks, an engine typically powers a generator to produce electrical energy for the at least one electric motor. In larger vehicles, such as heavy duty on-highway trucks, electrical energy may be produced utilizing a turbine disposed in fluid communication with engine exhaust, and the turbine being mechanically connected to a generator. For example, the turbine and the generator may reside on a common shaft. The generator generates electrical energy that may be used to power at least one electric motor that provides torque supplied to a transmission of the truck. The transmission of the truck also receives torque generated by the internal combustion engine to move the truck.
FIG. 1 schematically shows an existing hybrid electric vehicle 10. The hybrid electric vehicle 10 comprises an internal combustion engine 12, such as a diesel engine, and exhaust turbine and generator 14, a power distribution unit 16, electrical converter electronics 18, electric motor 20, and a transmission 22. The diesel engine 12 generates torque that is supplied to the transmission 22, and also generates exhaust gas that is utilized by the exhaust turbine and generator 14 to generate electrical energy. Electrical energy generated by the exhaust turbine and generator 14 is supplied to the power distribution unit 16, which allows electrical energy to be distributed to the electrical converter electronics 18, and the electric motor 20. The power distribution unit 16 additionally may direct electrical energy to a storage battery and resistor bank 24. The storage battery and resistor bank 24 receive power when the exhaust turbine and generator 14 is producing more electrical energy than is required by the electric motor 20, such as when motion of the vehicle is stopped, or the vehicle is coasting. However, the storage battery and resistor bank 24 add weight to the truck, therefore reducing by a same amount a quantity of cargo that may be legally hauled by the truck. Additionally, once the storage battery, or other electrical energy storing devices, is full, a resistor bank of the storage battery and resistor bank 24 is activated to use excess electrical energy. In situations where the resistor bank is activated, the resistors convert electrical energy to heat that is simply released to the atmosphere, thus, the electrical energy performs no useful work.
Therefore, a need exists for an exhaust turbine generator system that does not require storage of electrical energy.